Coupling light to higher order transverse modes of a near-concentric optical cavity

In the near-concentric regime, the transverse modes of an optical cavity have small mode volumes with a beam waist on the order of the atomic cross section. This shows potential for strong interaction between single atoms and light, which is a key component in distributed quantum computing architectures [1] . Furthermore, with centimetresized near-concentric cavities, the frequency spacing of the transverse modes ranges from tens of MHz to a GHz, matching well with the hyperfine or the Zeeman level splitting of an atom [2] . This near-degeneracy in resonant frequencies close to the critical point allows to explore the physics of atomic nonlinearities with multiple photonic modes strongly coupled to different hyperfine or magnetic energy levels of a quantum emitter.